Effects of Dietary Calcium and Non-Phytate Phosphorus Intake and Genetic Line on Reproductive Performance and Calcium and Phosphorus Digestibility in Broiler Breeder Hens and their Progeny

Background and Objective: The calcium (Ca) and non-phytate phosphorus (NPP) requirements of broiler breeder hens are less well characterized than those of laying hens, and whether these requirements differ among genetic lines remains unclear. This study evaluated the effects of dietary Ca and NPP intake and genetic line on reproductive performance, egg composition and Ca and P digestibility in broiler breeder hens and their progeny. Materials and Methods: Hens from four purelines (A to D; 40 hens per line) were individually caged and assigned to 1 of 6 diets from housing through 50 weeks of age in a 4×6 factorial arrangement. Diets contained 2.25 to 3.25% Ca with 0.25% NPP, or 3.25% Ca with 0.40% NPP. At peak feed allocation, these concentrations provided 3.08 to 4.45 g Ca and either 340 or 550 mg NPP/hen/day. Reproductive performance, egg components, hatchability and mineral digestibility were evaluated in hens, and Ca and P digestibility were subsequently evaluated in 14-day-old progeny fed a common starter diet. Results: Genetic line affected body weight, mortality, age at first egg, egg production, egg components, hatchability, and day-old progeny weight (p<0.05), whereas diet affected only day-old progeny weight (p = 0.002). Albumen and yolk accounted for 57.4 to 59.3% and 31.8 to 34.4% of egg weight, respectively, across genetic lines, while hatchability of fertile eggs ranged from 74.0 to 86.3% (p = 0.04); neither trait was affected by diet. Increasing dietary Ca and NPP increased excreta Ca and P concentrations (p<0.0001) and decreased P digestibility in hens from 38.5 to 28.3% (p = 0.0131), whereas Ca digestibility was unaffected. In 14-day-old progeny fed a common starter diet, dam genetic line affected all four excreta mineral and digestibility traits (p<0.0001). Calcium digestibility ranged from 17.4 to 48.8% among progeny from different dam lines, whereas maternal diet affected progeny P digestibility only when the maternal diet contained 0.40% NPP. Conclusion: Dietary Ca intake as low as 3.08 g/hen/day supported reproductive performance comparable to that achieved with higher Ca intakes under the conditions of this study. Increasing NPP intake from 340 to 550 mg/hen/day did not improve hen performance or Ca digestibility and reduced P digestibility. Differences in progeny mineral utilization were primarily associated with dam genetic line rather than maternal dietary Ca and NPP, suggesting that genetic factors may play a greater role than maternal diet in determining mineral utilization by progeny.